The present invention generally relates to a cleaning apparatus for precision cleaning of various products made of semiconductor, glass, plastic, metal, etc., such as an IC (Integrated Circuit) wafer, a semiconductor wafer of the IC wafer, a liquid crystal panel, a glass substrate of the liquid crystal panel, a plasma display, a glass substrate of the plasma display, an optical device, an optical fiber, precision components (metal precision components) for semiconductor, or the like, and more particularly relates to a cleaning apparatus for precision cleaning of such products using a cleaning brush and an ultrasonic vibrator.
For the precision processing of substrates such as glass substrates for a semiconductor wafer, a liquid crystal panel, etc., is generally performed in the following manner. Wires, an insulating film, and a film such as a semiconductor layer, etc., are formed, and the structure as desired is produced by a similar technique to the photographic printing technique, called photolithography. However, when performing precision processing by photolithography, the problem arises in that particulate contaminant (dust particles) adhering to the surface of the substrate causes defects such as disconnection, shorting, and inferior patterning, which lower the yield.
Therefore, conventionally, the substrate is always subjected to the precision cleaning before precision-processing it by the photolithography, and for this precision cleaning of the substrate, various cleaning apparatuses have been proposed.
In the conventional cleaning apparatus, a brush cleaning vessel and an ultrasonic cleaning vessel are provided separately, and a brush scrubbing cleaning and an ultrasonic cleaning are performed independently in the brush cleaning vessel and the ultrasonic cleaning vessel respectively. For this structure, the conventional cleaning apparatus is required to have a large size, and a large footprint (area of the bottom surface of the apparatus).
As an example of such conventional cleaning apparatus, a conveyer-type single wafer cleaning apparatus will be explained in reference to FIG. 5 and FIG. 6.
This type of conventional cleaning apparatus is provided with a brush cleaning vessel 101 illustrated in FIG. 5. As illustrated in FIG. 5, the brush cleaning vessel 101 includes a roll brush 102 for cleaning a substrate 110, shower nozzles 103 for blowing an aqueous cleaning agent 111 against the substrate 110 for shower-cleaning, and transport rollers 104 for transporting the substrate 110 in a horizontal direction.
The roll brush 102 has a rotation mechanism (not shown) and scrubs the upper surface of the substrate 110 while rotating thereon for brush cleaning. The shower nozzles 103 are provided for applying the aqueous cleaning agent 111 onto the surface of the substrate 110 by blowing thereto the aqueous cleaning agent 111 and also for shower-cleaning the surface of the substrate 110. The transport rollers 104 are provided for transporting the substrate 110 in the horizontal direction while rotating on the lower surface of the substrate 110. The brush cleaning vessel 101 is provided in the cleaning apparatus as an independent vessel. After the brush cleaning is performed in the cleaning vessel 101, the substrate 110 is placed in the ultrasonic cleaning vessel 105 illustrated in FIG. 6 for the subsequent ultrasonic cleaning.
As shown in FIG. 6, the ultrasonic cleaning vessel 105 includes an ultrasonic nozzle 106 for ultrasonically cleaning the substrate 110 from thereabove, and transport rollers 107 for transporting the substrate 110 in the horizontal direction.
The ultrasonic nozzle 106 blows the aqueous cleaning agent 111 from its leading end against the upper surface of the substrate 110 and ultrasonically vibrates the aqueous cleaning agent 111 by means of an ultrasonic vibrator (not shown) stored therein, thereby ultrasonically cleaning the upper surface of the substrate 110. The transport rollers 107 are provided for transporting the substrate 110 in the horizontal direction while rotating on the lower surface of the substrate 110.
As described, in the conventional cleaning apparatus, the brush scrubbing cleaning and the ultrasonic cleaning are performed in different vessels respectively. However, in the conventional cleaning apparatus of the foregoing structure, the removal of particulate contamination (dust particles) to the sufficient level of cleanliness cannot be ensured. Moreover, an overall footprint area of the cleaning apparatus becomes larger.
In response, another cleaning apparatus has been proposed wherein brush cleaning and ultrasonic cleaning are performed in the same vessel.
For example, Japanese Unexamined Patent Publication No. 87288/1999 (Tokukaihei 11-87288) published on Mar. 30, 1999 discloses a substrate cleaning apparatus wherein a cleaning brush and an ultrasonic nozzle are provided in parallel on one side of the substrate, so that the brush scrubbing cleaning and the ultrasonic cleaning can be performed simultaneously to effectively remove from the surface of the substrate the particulate contamination (dust particles) as well as fiber particles released from the cleaning brush.
Japanese Unexamined Patent Publication No. 86222/1995 (Tokukaihei 7-86222) published on Mar. 31, 1995 discloses another substrate cleaning apparatus wherein a cleaning brush and an ultrasonic nozzle are provided adjacently to improve the cleaning power of the substrate and at the same time to suppress the contamination of the cleaning brush.
Japanese Unexamined Patent Publication No. 5577/1994 (Tokukaihei 6-5577) published on Jan. 14, 1994 discloses still another substrate cleaning apparatus which performs a brush scrubbing cleaning in a cleaning vessel, wherein an overflow vessel storing therein an ultrasonic vibrator is adopted as a cleaning vessel to eliminate the problem of the contamination of the cleaning brush.
However, according to the cleaning apparatus of Japanese Unexamined Patent Publication No. 87288/1999, the cleaning brush and the ultrasonic nozzle always clean different parts of the substrate as is clear when thinking about only one particular part on the surface of the substrate. Specifically, for example, immediately after the cleaning brush has passed on the part for the brush cleaning, the ultrasonic nozzle passes that part for the ultrasonic cleaning. Therefore, precisely speaking, these two kinds of cleaning system are not applied to one part simultaneously but sequentially in a short time.
The foregoing structure merely offers an effect as achieved by reducing the switch time from the brush cleaning to the ultrasonic cleaning, i.e., the likelihood of the problem that the fibrous particles adhering to the substrate are dried and become difficult to be removed from the surface of the substrate can be suppressed. In this structure, however, an improvement in removing power of particulate contamination (dust particles) as well as an improvement in suppressing a reduction in yield due to the particulate contamination (dust particles) can be hardly expected as compared to the aforementioned cleaning apparatus of the structure wherein the brush cleaning and the ultrasonic cleaning are performed independently in different vessels. Therefore, the foregoing cleaning apparatus cannot provide a sufficient level of cleanliness to meet the increasing demand for cleaning of an improved precision (fineness).
Moreover, in the foregoing structure, the cleaning brush and the ultrasonic nozzle are provided in parallel on the same plane, and thus the cleaning brush itself is not subjected to the ultrasonic cleaning. Therefore, the longer is the operation time of the cleaning apparatus, the more is likely that the cleaning brush takes in the particulate contamination (dust particles) once removed out of the substrate surface, and such contamination once captured by the cleaning brush are redeposited on the surface of the substrate. Therefore, for the foregoing conventional apparatus, periodic maintenance operations are needed for cleaning the cleaning brush, such as cleaning the brush by taking it out of the apparatus, etc., in order to prevent the above problem. However, for the maintenance operations, it is required to stop the operation of the cleaning apparatus, and perform troublesome and time consuming operations, resulting in efficient cleaning.
In summary, the cleaning apparatus of Japanese Unexamined Patent Publication No. 87288/1999 has the following deficiencies.
1. Firstly, although the cleaning brush and the ultrasonic nozzle are driven simultaneously, because these members are provided on the same surface of the substrate, the brush scrubbing cleaning and ultrasonic cleaning can never be applied to the same part simultaneously. Namely, although the cleaning brush and the ultrasonic nozzle are driven simultaneously, the brush scrubbing cleaning and the ultrasonic cleaning can never be applied to the same part on the substrate surface simultaneously. Therefore, an improvement in removing power for the fibrous particles released from the cleaning brush does not lead to an improvement in removing power for the particulate contamination (dust particles). Therefore, the foregoing cleaning apparatus cannot provide a sufficient level of cleanliness to meet the increasing demand for cleaning of an improved precision (fineness).
2. Secondly, in the structure wherein the cleaning brush and the ultrasonic nozzle are provided in parallel on the same plane, the cleaning brush cannot be cleaned in the normal operation of the cleaning apparatus. Therefore, the troublesome maintenance operations are required for the cleaning of the cleaning brush.
The foregoing cleaning apparatus of Japanese Unexamined Patent Publication No. 86222/1995 also has the following problem. That is, in the structure wherein the ultrasonic nozzle is provided on the side of the cleaning brush, the ultrasonic wave and the aqueous cleaning agent supplied from the ultrasonic nozzle have difficulty reaching the part to be brush-cleaned on the surface of the substrate that is being disturbed by the cleaning brush. Therefore, the ultrasonic cleaning is specifically applied to the part surrounding the cleaning brush, and is hardly applied to the part to be brush-cleaned on the surface of the substrate.
The foregoing cleaning apparatus is provided with an ultrasonic nozzle for cleaning the cleaning brush. However, it is still difficult for the aqueous cleaning agent or the ultrasonic wave as supplied from the ultrasonic nozzle to reach the central part of the cleaning brush. Therefore, the cleaning of the cleaning brush by the ultrasonic nozzle is applied only to the side of a disk brush (cleaning brush), not to the central part of the disk brush. As a result, the particulate contamination (dust particles) is liable to remain in the central part of the disk brush, and the contamination of the substrate is liable to occur.
Moreover, in the foregoing cleaning apparatus, the aqueous cleaning agent and the ultrasonic wave supplied through the ultrasonic nozzle are reflected from the surface of the substrate to be incident on the surface of the cleaning brush. Therefore, in the state where the substrate is not set in the cleaning apparatus, neither of the aqueous cleaning agent nor ultrasonic wave supplied from the ultrasonic nozzle reaches the cleaning brush. Namely, in this structure, the cleaning brush is subjected to the ultrasonic cleaning only in the state where the substrate is set in the cleaning apparatus. Therefore, the particulate contamination (dust particles) removed from the cleaning brush may be redeposited onto the surface of the substrate, which in turn contaminates the substrate surface.
In summary, the cleaning apparatus of Japanese Unexamined Patent Publication No. 86222/1995 has the following deficiencies.
1. Firstly, only the part surrounding the cleaning brush is cleaned ultrasonically, and the part to be brush-cleaned on the substrate surface is hardly cleaned ultrasonically. Namely, although the cleaning brush and the ultrasonic nozzle are driven at the same time, the brush cleaning and ultrasonic cleaning never be applied to the same part simultaneously. Therefore, the foregoing cleaning apparatus cannot provide a sufficient level of cleanliness to meet the increasing demand for cleaning of an improved precision (fineness).
2. Secondly, cleaning of the cleaning brush by the ultrasonic nozzle is performed only on its side face of the cleaning brush, not in the central portion thereof.
3. Thirdly, the cleaning of the cleaning brush is performed only in the state where the substrate is set in the cleaning apparatus, and thus the particulate contamination (dust particles) once captured by the cleaning brush is liable to redeposite on the substrate.
In order to overcome the foregoing problem of the contamination of the cleaning brush associated with the structure wherein the cleaning of the cleaning brush is performed in the cleaning vessel, a substrate cleaning apparatus wherein an overflow vessel which stores therein a ultrasonic vibrator is adopted as the cleaning vessel has been proposed.
Further, Japanese Unexamined Patent Publication No. 5577/1994 discloses the brush cleaning structure wherein an overflow vessel which stores therein an ultrasonic vibrator is provided for soaking therein the cleaning brush and the substrate. With this structure, the cleaning brush and the substrate are always subjected to cleaning.
However, in the foregoing cleaning structure of soaking the cleaning brush and the substrate, compared with the case of blowing the aqueous cleaning agent through the nozzle, the flow of the cleaning agent is slow. Therefore, the aqueous cleaning agent in this cleaning structure of soaking is liable to stay in the overflow vessel, and dust particles as removed from the substrate float on the surface of the aqueous cleaning agent. Furthermore, due to this gentle flow of the aqueous cleaning agent, the dust particles are liable to float on the surface of the aqueous cleaning agent without being discharged, and such dust particles floating on the surface of the aqueous cleaning agent may redeposite on the surface of the substrate, which causes a serious problem in cleaning the substrate. Therefore, with the foregoing structure, although a deterioration in cleaning brush overtime may be suppressed, the substrate cannot be cleaned at a sufficient level of cleanliness. Therefore, the foregoing cleaning apparatus cannot provide a sufficient level of cleanliness to meet the increasing demand for cleaning of an improved precision (fineness).
Furthermore, according to the above structure, the cleaning brush is always washed, and for this reason, the aqueous cleaning agent cannot be kept clean as being always contaminated with the dust particles as removed from the cleaning brush. As a result, the precision cleaning cannot be performed at a sufficient level of cleanliness.
In summary, the cleaning apparatus of Japanese Unexamined Patent Publication No. 5577/1994 has the following deficiencies:
1. Firstly, since the cleaning brush and the substrate are soaked in the aqueous cleaning agent, the dust particles as removed from the substrate are liable to float on the surface of the aqueous cleaning agent, and redeposite onto the surface of the substrate. Therefore, although the deterioration of the cleaning brush over time may be suppressed to some extent, the cleaning power for the substrate would be lowered on the contrary. Therefore, the foregoing cleaning apparatus cannot provide a sufficient level of cleanliness to meet the increasing demand for cleaning of an improved precision (fineness).
2. Secondly, as the cleaning brush is always subjected to cleaning, the aqueous cleaning agent cannot be kept clean. It is therefore not possible to perform precision cleaning at a sufficient level of cleanliness.
It is an object of the present invention to provide a cleaning apparatus which permits a precision cleaning of an object to be cleaned with simplified maintenance operations, and which permits a reduced foot print area.
In order to achieve the above object, a cleaning apparatus of the present invention is characterized by comprising:
scrubbing means for scrubbing a surface of an object to be cleaned; and
ultrasonic wave projection means for supplying an aqueous cleaning agent against the surface of the object to be cleaned and generating an ultrasonic wave,
wherein the scrubbing means and the ultrasonic wave projection means are provided so as to oppose one another, and
the object to be cleaned is to be set between the scrubbing means and the ultrasonic wave projection means.
According to the foregoing structure, the scrubbing cleaning by the scrubbing means and the ultrasonic cleaning with an ultrasonic wave propagated from the ultrasonic wave projection means through the object to be cleaned are applied to the part to be scrubbed with the scrubbing means on the surface of the object to be cleaned simultaneously. By applying the scrubbing cleaning and the ultrasonic cleaning to the same part on the surface of the object to be cleaned, precision cleaning can be performed at a sufficient level of cleanliness.
According to the foregoing structure, the scrubbing means can be ultrasonically cleaned by the scrubbing means in a state where the object to be cleaned is not set in the cleaning apparatus by applying thereto the aqueous cleaning agent and the ultrasonic wave from the ultrasonic wave projection means. It is therefore possible to maintain the scrubbing means clean without taking it out from the cleaning apparatus, and thus troublesome maintenance operations can be omitted. Furthermore, since the scrubbing means is subjected to cleaning in the state where the object to be cleaned is not set in the cleaning apparatus, the likelihood of such problem that the particulate contamination (dust particles) once removed out of the scrubbing means are redeposited onto the object to be cleaned can be prevented, which is liable to occur when cleaning the scrubbing means in the state where the object to be cleaned is set in the cleaning apparatus.
Furthermore, in the foregoing structure, by integrating the scrubbing means and the ultrasonic wave projection means in one part, an overall footprint area of the cleaning apparatus can be reduced.
Therefore, according to the foregoing structure of the cleaning apparatus, precision cleaning of both the object to be cleaned and the scrubbing means can be performed at high level of cleanliness, and at the same time, an overall foot print area can be reduced.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.